Method and apparatus for sorting elements

Abstract

The present invention pertains to a method for sorting. The method comprises the steps of forming a decision tree comprised of at least a first level having at least a first entry with either a first result or a second result corresponding to values as they fill a queue. Then, there is the step of reading the result in the first entry of the first level of the decision tree. Next, there is the step of choosing the value in the first entry of the first level from the queue corresponding to the result in the first entry. The present invention comprises a priority queue. The priority queue comprises an array in which elements are stored. Also, the priority queue comprises a controller which stores the elements in the array with no memory reads and a constant number of memory writes so a smallest element in the array can be identified.

Claims

1. A method for sorting comprising the steps of:

forming a decision tree comprised of at least a first level having at least a first entry with either a first result or a second result corresponding to values as they fill a queue;

reading the result in the first entry of the first level of the decision tree; and

choosing the value from the queue corresponding to the result in the first entry.

2. A method for sorting comprising the steps:

forming a decision tree comprised of N levels, where N.gtoreq.-1 and is an integer and corresponds to a queue of 2.sup.N elements each having a value, as the queue is filled, each level L having 2.sup.L entries where L.gtoreq.0 and is an integer, each entry having either a first result or a second result corresponding to values in the queue;

reading the results in the entry of the 0th level;

reading the results in the entries of subsequent higher levels, if any, depending on the result read in a previous lower level; and

choosing the value from the queue corresponding to the result in the entry in a highest level.

3. A method as described in claim 2 wherein L.gtoreq.1 and wherein the step of reading the results in the entries of the subsequent higher levels includes the step of reading the entry in the first level depending on the result in the entry in the 0th level; and wherein the choosing step includes the step of choosing the value from the queue corresponding to the result read in the entry of the first level.

4. A method as described in claim 3 wherein the forming step includes the steps of writing a first value into the first element of the queue;

writing a second value into the second element of the queue;

comparing the second value with the first value;

writing the first result or second result into a corresponding entry of the first level for the corresponding elements depending on whether the first value is greater than or less than the second value, respectively; and

repeating the step of writing, comparing and writing a third value in regard to the second value and a corresponding entry; and

comparing the third value to the smallest of the first and second values, and writing the first result or second result into a corresponding entry of the 0th level for the corresponding elements depending on whether the third value is greater than or less than the second value, respectively.

6. A priority queue comprising:

a memory in which elements are stored; and

a controller which stores the elements in the memory with no memory reads and a constant number of memory writes so a smallest element in the memory can be identified, said controller connected to the memory.

7. A priority queue as described in claim 6 wherein the memory includes a register file having a decision tree and a comparison list.

8. A method for manipulating elements comprising the steps of:

storing a first element having a value in a first queue location in an element queue having a size which stores 2.sup.N elements, where N.gtoreq.2 and is an integer;

updating in a register how many elements are in the queue and the value of the first element;

storing a second element having a value in a second queue location of the element queue contiguously with the first element;

updating in the register how many elements are in the queue and the value of the second element;

comparing the value of the second element with the value of the first element to yield a first comparison result corresponding to which value of the first and second elements is larger;

storing a first comparison result in a first location of a plurality of locations of a decision tree, said plurality of locations corresponding to a plurality of levels;

updating a first comparison element of a plurality of comparison elements of a comparison list array, each comparison element associated with a level of the plurality of levels, the comparison element updated corresponding to the second queue location of the element queue in which the second element is stored and in the first queue location of the element queue in which the first element is stored;

storing a third element having a value in a third queue location in the element queue contiguously with the second elements;

updating in the register how many elements are in the queue and the value of the third element;

comparing the value of the third element with the value of the first and second elements which is smaller to yield a second comparison result corresponding to which value of the first and second elements and the third element is smaller;

storing the second comparison result in a second location of the decision tree;

updating a second comparison element corresponding to the third queue location in which the third element is stored;

storing a fourth element having a value in a fourth queue location in the element queue contiguously with the third element;

updating in the register how many elements are in the queue and the value of the fourth element;

comparing the value of the fourth element with the third element to yield a third comparison result corresponding to which value of the third and fourth elements is smaller;

storing the third comparison result in a third location of the decision tree;

comparing the value of the third element and fourth element which is smallest with the value of the first element and second element which is smallest to yield a fourth comparison result corresponding to which value of the first, second, third or fourth elements is smaller;

storing the fourth comparison result in the second location of the decision tree;

updating the comparison list;

changing the value of the third element in the element queue to a new value;

comparing the new value to the value of the fourth element to yield a fifth comparison result;

storing the fifth comparison result in the third location of the decision tree;

comparing the fifth comparison result with the first comparison result of the decision tree to obtain a sixth comparison result;

storing the sixth comparison result in the second location of the decision tree;

updating the comparison list;

finding the queue location in the element queue which has the smallest value by only reading the comparison result in the decision tree; and

obtaining the smallest value.